Summary

The presented paper evaluates how coastal ice opening events in the sea ice of the southern Beaufort Sea (SBS) in spring 2021 modulate the efficiency of wind forcing on sea-ice drift and the associated transport of multiyear sea ice towards the Chukchi Sea. It is hypothesized, that coastal openings favour the free drift of sea ice in the SBS and thereby potentially contribute to the observed annual losses of MYI. The authors use remote sensing data (combined MODIS/AMSR2) to identify sea-ice opening events, i.e. flaw leads, a SIDEx buoy array as well as Polar Pathfinder sea-ice drift data to track the transport of ice and ERA5 reanalysis data to derive associated atmospheric conditions.  The goal of the presented research is to relate sea-ice drift in the SBS to coastal ice opening events and identify potential implications for Arctic multi-year ice loss.

General comments and decision

The paper presents a well-written study with a meaningful structure that is nice to follow by the reader. The presentation of the results is well thought out and the discussion is placed in good context with current research. Also, the supplements provide a valuable add-on to the presented results. However, I think the paper in its present form needs to be strengthened in pointing out what new lessons were learned and in how far these are important for moving our understanding forward in this field. It is a well-documented and detailed case study of sea-ice dynamics in the Beaufort Sea in spring 2021, which finally misses to embed its findings into a meaningful longer-term context. Although the introduction and discussion aim to connect to this context, the limitation to derive coastal openings and associated drift patterns for a period of 2 months only represents a weakness of this paper (how special was 2021 in terms of opening events?). This work would gain strength and meaning if at least ice opening events were analysed on longer time scales (trends?) and then compared to what was happening in 2021.

Another major concern I have is that the paper postulates a causal relationship between ice opening events and free ice drift in the SBS, which I think is a misleading concept.  I think that the factor that drives both, flaw lead formation and free ice drift, is wind direction and wind speed in combination with coastal geometry, which has been shown also in other papers investigating flaw lead and polynya dynamics. While this relationship is documented and mentioned in the submitted paper, the free ice drift events are finally explained by the occurrence of sea-ice opening events, which I think is a bit confusing. In this context I also think that the title of the paper should be adjusted.

Detailed comments

The terms “lead opening events” and “ice opening events” are both used to describe the same process. Please consider using only one.

Page 4, bottom: I don’t think it needs this equation if the approach is described in the text.

L103 ff: [“Physically, this …”]. I think this statement needs a better explanation or reference (other than WMO) and that the value of 200m is highly sensitive to the amount of thin ice in the leads.

L118: “SIC-derived area with opening…” Not clear, what exactly is meant.

Figure 5: Can buoy positions be shown in 5k?

L274: What was the average wind direction for compact and open days?

Figure 6 is quite small. Can it be widened?

Figure 9 Please show where this regional subset (c-f) is located in the study area (Fig. 2).

 L 413: “…usually remained quite high…” Can that be shown here?

Summary:

This paper analyzes the drift of a tight array of GPS buoys in the Southern Beaufort Sea in response to wind speed and direction. This paper is generally well written, and I recommend acceptance after very minor revisions. Most of my comments are suggestions on grammar and style.

Details:

1)    Lines 12 and 15: These sentences imply that lead opening causes increases SBS ice motion, but I would argue that both the lead opening and increased ice motion are both a consequence of favorable winds away from the coast. I suggest rewriting this as “These results quantify the disproportionate contribution in offshore winds towards breaking the sea ice away from the coast, lead opening and SBD ice transport during Spring 2021, …”. While this idea may not be new, this paper discusses these processes in wonderful detail that warrants publication of these results.

2)    Line 48: suggest rewriting this as "The consolidated season in the Beaufort Sea extended through March and April 2021..." Since the subject here is the "consolidated season", rather than March and April.

3)    Line 50: Delete “During the consolidated season, “. Too wordy.

4)    Line 51: Change “Of sufficient magnitude, these internal stresses can”, to "The internal stresses can be of sufficient magnitude to cause the ice pack..."

5)    Lines 57-58: Rather than “that lose and remain”, I think the authors mean “that is loose and remains”.

6)     Tschudi et al. 2019b paper should be cited in Figure 1 caption or in the Data section.

7)    The first paragraphs of new sections aren’t indented. Is this the preferred style of the journal?

8)    Line 246: Suggest change “just” to “only”.

9)    Lines 296 and 301. I suggest West-Northwesterly rather than repeat the “erly” suffix.

10)    The supplemental movies are wonderful! Lots of insight/information buried in these beyond what is discussed in the paper. I can see these being used/cited in many papers/presentations on sea ice.